[media] v4l2-ctrls: add v4l2_ctrl_auto_cluster to simplify autogain/gain scenarios

It is a bit tricky to handle autogain/gain type scenerios correctly. Such
controls need to be clustered and the V4L2_CTRL_FLAG_UPDATE should be set on
the autofoo controls. In addition, the manual controls should be marked
inactive when the automatic mode is on, and active when the manual mode is on.
This also requires specialized volatile handling.

The chances of drivers doing all these things correctly are pretty remote.
So a new v4l2_ctrl_auto_cluster function was added that takes care of these
issues.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/v4l2-ctrls.c

@@ -39,6 +39,20 @@ struct ctrl_helper {
 	bool handled;
 };
 
+/* Small helper function to determine if the autocluster is set to manual
+   mode. In that case the is_volatile flag should be ignored. */
+static bool is_cur_manual(const struct v4l2_ctrl *master)
+{
+	return master->is_auto && master->cur.val == master->manual_mode_value;
+}
+
+/* Same as above, but this checks the against the new value instead of the
+   current value. */
+static bool is_new_manual(const struct v4l2_ctrl *master)
+{
+	return master->is_auto && master->val == master->manual_mode_value;
+}
+
 /* Returns NULL or a character pointer array containing the menu for
    the given control ID. The pointer array ends with a NULL pointer.
    An empty string signifies a menu entry that is invalid. This allows
@@ -643,7 +657,7 @@ static int ctrl_is_volatile(struct v4l2_ext_control *c,
 }
 
 /* Copy the new value to the current value. */
-static void new_to_cur(struct v4l2_ctrl *ctrl)
+static void new_to_cur(struct v4l2_ctrl *ctrl, bool update_inactive)
 {
 	if (ctrl == NULL)
 		return;
@@ -659,6 +673,11 @@ static void new_to_cur(struct v4l2_ctrl *ctrl)
 		ctrl->cur.val = ctrl->val;
 		break;
 	}
+	if (update_inactive) {
+		ctrl->flags &= ~V4L2_CTRL_FLAG_INACTIVE;
+		if (!is_cur_manual(ctrl->cluster[0]))
+			ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
+	}
 }
 
 /* Copy the current value to the new value */
@@ -1166,7 +1185,7 @@ void v4l2_ctrl_cluster(unsigned ncontrols, struct v4l2_ctrl **controls)
 	int i;
 
 	/* The first control is the master control and it must not be NULL */
-	BUG_ON(controls[0] == NULL);
+	BUG_ON(ncontrols == 0 || controls[0] == NULL);
 
 	for (i = 0; i < ncontrols; i++) {
 		if (controls[i]) {
@@ -1177,6 +1196,28 @@ void v4l2_ctrl_cluster(unsigned ncontrols, struct v4l2_ctrl **controls)
 }
 EXPORT_SYMBOL(v4l2_ctrl_cluster);
 
+void v4l2_ctrl_auto_cluster(unsigned ncontrols, struct v4l2_ctrl **controls,
+			    u8 manual_val, bool set_volatile)
+{
+	struct v4l2_ctrl *master = controls[0];
+	u32 flag;
+	int i;
+
+	v4l2_ctrl_cluster(ncontrols, controls);
+	WARN_ON(ncontrols <= 1);
+	master->is_auto = true;
+	master->manual_mode_value = manual_val;
+	master->flags |= V4L2_CTRL_FLAG_UPDATE;
+	flag = is_cur_manual(master) ? 0 : V4L2_CTRL_FLAG_INACTIVE;
+
+	for (i = 1; i < ncontrols; i++)
+		if (controls[i]) {
+			controls[i]->is_volatile = set_volatile;
+			controls[i]->flags |= flag;
+		}
+}
+EXPORT_SYMBOL(v4l2_ctrl_auto_cluster);
+
 /* Activate/deactivate a control. */
 void v4l2_ctrl_activate(struct v4l2_ctrl *ctrl, bool active)
 {
@@ -1595,7 +1636,7 @@ int v4l2_g_ext_ctrls(struct v4l2_ctrl_handler *hdl, struct v4l2_ext_controls *cs
 		v4l2_ctrl_lock(master);
 
 		/* g_volatile_ctrl will update the new control values */
-		if (has_volatiles) {
+		if (has_volatiles && !is_cur_manual(master)) {
 			for (j = 0; j < master->ncontrols; j++)
 				cur_to_new(master->cluster[j]);
 			ret = call_op(master, g_volatile_ctrl);
@@ -1633,7 +1674,7 @@ static int get_ctrl(struct v4l2_ctrl *ctrl, s32 *val)
 
 	v4l2_ctrl_lock(master);
 	/* g_volatile_ctrl will update the current control values */
-	if (ctrl->is_volatile) {
+	if (ctrl->is_volatile && !is_cur_manual(master)) {
 		for (i = 0; i < master->ncontrols; i++)
 			cur_to_new(master->cluster[i]);
 		ret = call_op(master, g_volatile_ctrl);
@@ -1678,6 +1719,7 @@ EXPORT_SYMBOL(v4l2_ctrl_g_ctrl);
    Must be called with ctrl->handler->lock held. */
 static int try_or_set_control_cluster(struct v4l2_ctrl *master, bool set)
 {
+	bool update_flag;
 	bool try = !set;
 	int ret = 0;
 	int i;
@@ -1717,14 +1759,17 @@ static int try_or_set_control_cluster(struct v4l2_ctrl *master, bool set)
 		ret = call_op(master, try_ctrl);
 
 	/* Don't set if there is no change */
-	if (!ret && set && cluster_changed(master)) {
-		ret = call_op(master, s_ctrl);
-		/* If OK, then make the new values permanent. */
-		if (!ret)
-			for (i = 0; i < master->ncontrols; i++)
-				new_to_cur(master->cluster[i]);
-	}
-	return ret;
+	if (ret || !set || !cluster_changed(master))
+		return ret;
+	ret = call_op(master, s_ctrl);
+	/* If OK, then make the new values permanent. */
+	if (ret)
+		return ret;
+
+	update_flag = is_cur_manual(master) != is_new_manual(master);
+	for (i = 0; i < master->ncontrols; i++)
+		new_to_cur(master->cluster[i], update_flag && i > 0);
+	return 0;
 }
 
 /* Try or set controls. */

include/media/v4l2-ctrls.h

@@ -65,6 +65,15 @@ struct v4l2_ctrl_ops {
   *		control's current value cannot be cached and needs to be
   *		retrieved through the g_volatile_ctrl op. Drivers can set
   *		this flag.
+  * @is_auto:   If set, then this control selects whether the other cluster
+  *		members are in 'automatic' mode or 'manual' mode. This is
+  *		used for autogain/gain type clusters. Drivers should never
+  *		set this flag directly.
+  * @manual_mode_value: If the is_auto flag is set, then this is the value
+  *		of the auto control that determines if that control is in
+  *		manual mode. So if the value of the auto control equals this
+  *		value, then the whole cluster is in manual mode. Drivers should
+  *		never set this flag directly.
   * @ops:	The control ops.
   * @id:	The control ID.
   * @name:	The control name.
@@ -105,6 +114,8 @@ struct v4l2_ctrl {
 	unsigned int is_new:1;
 	unsigned int is_private:1;
 	unsigned int is_volatile:1;
+	unsigned int is_auto:1;
+	unsigned int manual_mode_value:5;
 
 	const struct v4l2_ctrl_ops *ops;
 	u32 id;
@@ -363,6 +374,40 @@ int v4l2_ctrl_add_handler(struct v4l2_ctrl_handler *hdl,
 void v4l2_ctrl_cluster(unsigned ncontrols, struct v4l2_ctrl **controls);
 
 
+/** v4l2_ctrl_auto_cluster() - Mark all controls in the cluster as belonging to
+  * that cluster and set it up for autofoo/foo-type handling.
+  * @ncontrols:	The number of controls in this cluster.
+  * @controls:	The cluster control array of size @ncontrols. The first control
+  *		must be the 'auto' control (e.g. autogain, autoexposure, etc.)
+  * @manual_val: The value for the first control in the cluster that equals the
+  *		manual setting.
+  * @set_volatile: If true, then all controls except the first auto control will
+  *		have is_volatile set to true. If false, then is_volatile will not
+  *		be touched.
+  *
+  * Use for control groups where one control selects some automatic feature and
+  * the other controls are only active whenever the automatic feature is turned
+  * off (manual mode). Typical examples: autogain vs gain, auto-whitebalance vs
+  * red and blue balance, etc.
+  *
+  * The behavior of such controls is as follows:
+  *
+  * When the autofoo control is set to automatic, then any manual controls
+  * are set to inactive and any reads will call g_volatile_ctrl (if the control
+  * was marked volatile).
+  *
+  * When the autofoo control is set to manual, then any manual controls will
+  * be marked active, and any reads will just return the current value without
+  * going through g_volatile_ctrl.
+  *
+  * In addition, this function will set the V4L2_CTRL_FLAG_UPDATE flag
+  * on the autofoo control and V4L2_CTRL_FLAG_INACTIVE on the foo control(s)
+  * if autofoo is in auto mode.
+  */
+void v4l2_ctrl_auto_cluster(unsigned ncontrols, struct v4l2_ctrl **controls,
+			u8 manual_val, bool set_volatile);
+
+
 /** v4l2_ctrl_find() - Find a control with the given ID.
   * @hdl:	The control handler.
   * @id:	The control ID to find.